The Prophet ﷺ used to say salam to his right and to his left: As-salamu 'alaykum wa rahmatullah, as-salamu alaykum wa rahmatullah (peace be upon you and the mercy of Allah, peace be upon you and the mercy of Allah) until the whiteness of his cheek could be seen from here, and the whiteness of his cheek from here.
عَنِ النَّبِيِّ ﷺ أَنَّهُ كَانَ يُسَلِّمُ عَنْ يَمِينِهِ وَعَنْ يَسَارِهِ السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللَّهِ السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللَّهِ حَتَّى يُرَى بَيَاضُ خَدِّهِ مِنْ هَا هُنَا وَبَيَاضُ خَدِّهِ مِنْ هَا هُنَا